# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def isSameTree(self,p,q):
        if p is None or q is None:
            return p is q
        return p.val == q.val and self.isSameTree(p.left,q.right) and self.isSameTree(p.right,q.left)
    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
        return self.isSameTree(root.left,root.right)

    